Mandrel-protecting device for coldpilger rolling mills



May 26, 1959 F. ZEUNERT ET AL 2, MANDREL-PROTECTING DEVICE FORCOLD-PILGER ROLLING MILLS Filed 001:. 28, 1957 of the breakdowns whichoccur in Fritz Zeunert, M. Gladbach, and Heinz Buchholz, Dusseldorf,Germany, assignors to Mannesmann-Meer Akfiengesellschaft, M. Gladbach,Germany Application October 28, 1957, Serial No. 692,794 1 Claim. (Cl.80-11) The invention concerns a mandrel-protecting device forcold-pilger tube rolling mills. By far the largest part the operation ofcoldpilger rolling mills is caused by the breaking of the mandrel overwhich the tube is being drawn. These breakages of the mandrels occur inthe part of the cone of the mandrel most subjected to stress. The frontend of the mandrel freed when the mandrel rod is thus broken is freelypulled between the barrels of the rolls of the machine which keeps onrunning. This forcibly pushes the rolls apart resulting in considerabledanger to the entire roll stand.

Mandrel-protecting devices have been known. In one device a thin feelerrod is held at the front end of the mandrel ahead of it at apredetermined distance, about 5 cm. This rod leads through the issuingfinished tube. It operates a terminal switch located at the end of thedischarge channel, it the end of the mandrel breaks and migrates morethan a certain distance in the direction of the discharge side.Actuation of the end switch causes disconnection of the main motor. Inanother device a hydraulic roll-safety device is provided which, in thecase of an excess roll pressure produced by pulling in the broken end ofthe mandrel between the rolls makes possible a turning aside of therolls. This is done by the hydraulic cylinders located on the roll standand, by means of suitable valves, adjusted to a definite rollingpressure, in the case of excessive pressure, blow ofl, thereby makingpossible turning aside of the rolls. These known devices have thedrawback that, in the former, by the required pulling off of thefinished tubes over the safety rod, makes the operation of producingtubes difficult and in the case of high-speed cold-pilger machines,another operator is required. The second mentioned prior art arrangementoperates with a certain inertia, which, under certain circumstances,does not fully eliminate the moments of danger.

In the mandrel safety device according to the application, the precedingdrawbacks are avoided by displaceably providing shortly beyond the endof the mandrel outside the tube to be pilger-treated-preferably in thelongitudinal free end thereof--a radiation sender and a radiationreceiver. The latter is connected with a relay located in a circuitwhich influences the main motor switch and by equipping the end of themandrel with a. part not permeable to the rays used.

The arrangement of the parts and their mode of operation will be seen indetail in the drawings. In the drawings faf.

Figure 1 is a longitudinal diagrammatic view of the mandrel end, rollsand tube and their dimensional relations to the mandrel protectingdevice of our invention.

Fig. 2 is a view partly in vertical cross-section revolved 90 from theradiation line e-f of Fig. 1 of the mandrel protecting device andshowing the electric circuitry in diagram.

By means of a suitable radiation generator a located directly, i.e., afew millimeters prior to the discharge end of the rolling mandrel b whenin normal operating position, a radiation (e.g., X-rays) suitable topass through the material 0 to be rolled, is sent across the material.The radiation is in the form of a radiant beam e by means of alight-stop d in the generator a. This is made of suitable material suchas lead. After passing through the rolled tube c, this beam of radiantenergy 2 strikes a suitable receiver f inserted in an electrical circuitg containing a battery. In normal operation, this circuit is closed anda relay 11 therein is closed. The front end of the mandrel 1', while notinvolved directly in the drawing process proper is impermeable to theradiant energy e coming from the source of radiation a and which passesthrough the rolling material. This is achieved by attaching a lead headj to the end i of the mandrel b. The circuit also contains a relay hadapted to influence the main motor circuit (not shown) through suitableconnections.

Now, it, upon breaking of the mandrel, the mandrel end i moves in thedirection of movement of the material c being rolled, the beam of rays 2is interrupted by the lead head j and thereby the circuit g loses itselectrical potential. The relay h then opens up, thereby operatingthrough suitable connecting means the disconnection of the main drivingmotor of the cold-pilger rolling mill.

By the arrangement according to the present application, starting thedisconnecting process in case of mandrel breakage takes placepractically without inertia.

For adapting the mandrel-protecting device to all operationalrequirements, the apparatus is so attached to the rolling mill that itis movable in the direction of rolling (as indicated by the arrows inFigure 1) and is exactly adjustable to any desired position.

What is claimed is:

A mandrel-protecting device for a cold-pilger tube rolling mill,comprising a mandrel, a radiant energy generator and a radiant energydetector therefor adjustably mounted outside and on opposite sides ofthe tube being treated, closely beyond the end of the mandrel in thelongitudinal direction, in combination with an electric circuit in whichthe detector is located, a relay activated by that circuit, a main motorswitch influenced by that relay, and an end portion on the mandrelimpermeable to the radiant energy; whereby if the mandrel breaks theimpermeable end will be drawn into the path of the rays and the relaywill influence the main switch and stop the mill.

References Cited in the file of this patent UNITED STATES PATENTS2,264,725 Shoupp et a1. Dec. 2, 1941 2,685,216 Bannister et a1. Aug. 3,1954

